<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<span th:text="${param.fileName}"></span>
<a th:href="@{/file_down(fileName=${param.fileName},contentType=${param.contentType})}"
   th:text="${param.fileName}"></a>
</body>
</html>